Changes in lipid composition and respiratory activity of wheat roots treated with inhibitor of phosphoinositide cycle of lithium ions

A study was made of the effect of lithium ions (5 mM LiCl) on the growth and respiration of roots of 2-5 day old wheat seedlings, composition of phospholipids, free fatty acids and sterols, and superoxide radical generation. Significant growth depression was shown in roots treated with lithium, increasing with age of seedlings. The growth of seedlings on a 5 mM LiCl containing medium influenced the lipid composition in roots. In the roots of these seedlings phospholipid contents increased along with a decrease in free fatty acids, and the ratio of sterol/phospholipids, while superoxide radical production was stimulated. Lithium stimulated oxygen consumption of excised roots of 5 day old seedlings. Due to its physical and chemical properties lithium is supposed to be able to disrupt gradients of Ca2+, H+, K+, and to lead to a partial blockade of signal transduction for triggering proliferation via the phosphoinositide cycle. Changes in the lipid composition, increase in the membrane permeability for ions, and respiration of roots of seedlings grown in LiCl-containing medium are presumably associated with growth depression and juvenility of roots.     

Separating multiple, short-term, deleterious effects of saline solutions on the growth of cowpea seedlings

? Reductions in plant growth as a result of salinity are of global importance in natural and agricultural landscapes. ? Short-term (48-h) solution culture experiments studied 404 treatments with seedlings of cowpea (Vigna unguiculata cv Caloona) to examine the multiple deleterious effects of calcium (Ca), magnesium (Mg), sodium (Na) or potassium (K). ? Growth was poorly related to the ion activities in the bulk solution, but was closely related to the calculated activities at the outer surface of the plasma membrane, {I(z)}?°. The addition of Mg, Na or K may induce Ca deficiency in roots by driving {Ca2+}?° to < 1.6 mM. Shoots were more sensitive than roots to osmolarity. Specific ion toxicities reduced root elongation in the order Ca2+ > Mg2+ > Na+ > K+. The addition of K and, to a lesser extent, Ca alleviated the toxic effects of Na. Thus, Ca is essential but may also be intoxicating or ameliorative. ? The data demonstrate that the short-term growth of cowpea seedlings in saline solutions may be limited by Ca deficiency, osmotic effects and specific ion toxicities, and K and Ca alleviate Na toxicity. A multiple regression model related root growth to osmolarity and {I(z)}?° (R2=0.924), allowing the quantification of their effects.     

Effects of sodium chloride stress and calcium supply on growth, potassium uptake, and internal chloride and sodium levels of winter wheat seedlings

The effects of saline conditions on the K+ (86Rb), Na+ and Cl- uptake and growth of 6-day-old wheat (Triticum aestivum L. cv. GK Szeged) seedlings were studied in the absence and presence of Ca2+. It was found that on direct NaCl treatment the K+ uptake of the roots in the absence of Ca2+ declined significantly with increasing salinity. The reverse was true, however, in the case of NaCl pretreatment: seedlings grown under highly saline conditions (50 mM NaCl) absorbed more K+ than those pretreated with low levels of NaCl (1 or 10 mM NaCl). The data indicate a definite Na(+)-induced K+ uptake inhibition and/or feed-back regulation in the K+ uptake of roots under the above-mentioned growth conditions. As regards the Ca2+ effect, it was established that supplemental Ca2+ counteracts the unfavourable effect of saline conditions as concerns both the K+ uptake of the roots and the dry matter yield of the seedlings. The internal concentrations of Na+ and Cl- in the seedlings increased in proportion to increasing salinity. Marked differences were experienced, however, in the internal concentrations of Na+ and Cl- in the roots and shoots, respectively. It was concluded that under these experimental conditions the salt tolerance of wheat could be related to its capability of restricting the transport of Na+ at low and moderate levels to the shoots, where it is highly toxic.     

Ammonium inhibition of Arabidopsis root growth can be reversed by potassium and by auxin resistance mutations aux1, axr1, and axr2.

A novel effect of ammonium ions on root growth was investigated to understand how environmental signals affect organ development. Ammonium ions (3-12 mM) were found to dramatically inhibit Arabidopsis thaliana seedling root growth in the absence of potassium even if nitrate was present. This inhibition could be reversed by including in the growth medium low levels (20-100 microM) of potassium or alkali ions Rb+ and Cs+ but not alkali ions Na+ and Li+. The protective effect of low concentrations of potassium is not due to an inhibition of ammonium uptake. Ammonium inhibition is reversible, because root growth was restored in ammonium-treated seedlings if they were subsequently transferred to medium containing potassium. It is known that plant hormones can inhibit root growth. We found that mutants of Arabidopsis resistant to high levels of auxin and other hormones (aux1, axr1, and axr2) are also resistant to the ammonium inhibition and produce roots in the absence of potassium. Thus, the mechanisms that mediate the ammonium inhibition of root development are linked to hormone metabolic or signaling pathways. These findings have important implications for understanding how environmental signals, especially mineral nutrients, affect plant root development.     

亚适温条件下缺铁和硝酸盐胁迫对番茄幼苗生长及铁吸收的影响

研究亚适温(昼/夜18 ℃/12 ℃)条件下缺铁和硝酸盐胁迫对番茄幼苗生长及铁吸收的影响.结果表明: 与适温对照相比,亚适温条件下番茄幼苗生长受到明显的抑制,株高、叶面积显著变小,干物质积累下降;亚适温下缺铁对番茄幼苗生长的影响比适温下缺铁的影响大.亚适温条件下,缺铁、硝酸盐胁迫及二者同时胁迫的番茄幼苗株高与无胁迫处理差异不显著,但幼苗叶面积明显变小,电解质渗漏率、根系活力和三价铁还原酶活性明显增加,叶绿素含量降低;根总长、根表面积、根体积及根尖数明显减小;幼苗根、茎、叶中铁含量明显降低.亚适温下硝酸盐胁迫以及缺铁与硝酸盐二者同时胁迫加重了番茄幼苗干物质积累的减少、电解质渗漏率的增加,以及减少了对铁离子的吸收.Fe²⁺对K⁺和Ca²⁺吸收具有拮抗作用,不同器官中的表现有所差异;降低营养液中的Fe²⁺浓度可使番茄幼苗的缺铁症状更加严重.     

Mitotic index of meristematic cells and root growth of Pisum sativum is affected by inositol cycle modulators

Relationships between cell division and inositol cycle modulation caused by different effectors in roots of Pisum sativum were studied. Stimulation of the inositol cycle by myoinositol increased the mitotic index of meristematic cells and root length, while the inhibition of the cycle with Li+ and a heavy metal Gd3+ considerably decreased mitotic activity and growth. Exposure of roots to 10 mM CaCl2 and 15 mM myoinositol resulted in the accumulation of chromosome aberrations. Changes in the activity of inositol cycle are assumed to be involved in the root growth control.     

Nitrite in the root zone and its effects on ion uptake and growth of wheat seedlings

The immediate and posteffects of various concentrations of NaNO₂ on ion uptake of wheat ( Triticum aestivum L. cv. GK Öthalom) seedlings were studied at different pH values. Without pretreatment, the higher the concentration of NaNO₂ the greater was the decrease in uptake of K⁺ into the roots, both at pH 4 and pH 6. At pH 6 but not at pH 4 the reverse was true when the seedlings were pretreated with NaNO₂. Due to the high Na⁺ content of the roots, an effect of Na⁺ in this process cannot be excluded. Nitrite was taken up by the roots more rapidly than nitrate. Nitrite at 0.1 m M in the medium induced the development of an uptake system for both NO⁻₂ and NO⁻₃ in wheat roots. At higher concentrations pretreatment with NO⁻₂ decreased NO⁻₃ uptake by the roots, but NO₃ did not inhibit the uptake of NO₂. The toxic effect of NO⁻₂ was strongly pH dependent. Lower pH of the external solution led to an increased inhibition by NO⁻₂ of both ion uptake and growth of seedlings. The inhibitory effect of NO⁻₂ differed considerably for roots and shoots. The roots and especially the root hairs were particularly sensitive to NO⁻₂ treatment.     

Aluminum uptake and aluminum-induced rapid root growth inhibition of rice seedlings

Aluminum (Al) inhibits root growth in acidic soil, but the site of action of Al remains unclear. We investigated whether the rate of Al accumulation correlates to Al-indeced rapid root growth inhibition in rice seedlings (Oryza sativa L. cv. Youngnam). Growth of roots was significantly inhibited by 100 μM AICI₃, as early as 1 h after the treatment. The inhibition of root growth was strongly dependent on Al concentration (l₅₀ = 20 (μM) and Al-exposure time (l₅₀ = 23 min at 25 μM Al) in a solution of 10 mM KCI and 1 mM CaCl₂ buffered by 10 mM Mes/KOH (pH 4.5). Using ICPES, massive uptake of Al by roots was observed even at 15 min treatment of 25 μM Al. The kinetics of Al uptake by the roots closely corresponded to the inhibitory effects of Al on root growth. When the roots of seedlings were exposed to 50 (μM Al for 1 h, then sectioned and stained with hematoxylin, all cell types of the roots showed the presence of Al in the cytoplasm. These results indicate that Al was rapidly taken up into the root cells and thereby reduced root growth.     

Effect of calcium chloride on heavy metal induced alteration in growth and nitrate assimilation of Sesamum indicum seedlings

In the early growth phase of Sesamum indicum cv. PB-1, the decrease in fresh and dry mass was higher with 1.0 mM Cd²⁺ than with the same level of Pb²⁺ and Cu²⁺. Recovery from the metal stress was considerable in the root fresh weight and almost completely in the root dry weight when 10.0 mM (1.9 EC), calcium chloride was supplied to the growing seedlings along with the metal salts in various combinations. Accumulation of Pb²⁺, Cd²⁺ and Cu²⁺ was differential to the metals and the plant parts when supplied without or with 10.0 mM calcium chloride. The order of endogenous metal accumulation was Cu²⁺Cd²⁺Pb²⁺ and roots accumulated more metal than the leaves in the absence, as well as in the presence, of calcium chloride. Calcium chloride could recover loss of in vivo NRA in roots caused by either of the metal combinations, whereas the salt could recover the loss in leaf NRA caused only by Pb²⁺Cd²⁺ (1.0 mM each). Response of root and leaf NRA was on the other hand, different when the enzyme was assayed directly using an in vitro assay method, and the salt accelerated the loss in enzyme activity drastically. The organic-N content of root and leaf was, however, increased significantly (p < 0.001) with calcium chloride alone and with the metals supplied in various combinations. Our data indicate that instead of a high endogenous accumulation of Cu²⁺, Cd²⁺ and Pb²⁺ in roots and leaves the metal toxicity is recovered to a great extent in the presence of 10.0 mM calcium chloride in the root environment regarding growth and nitrate reduction of the roots and leaves of young sesame seedlings.     

Effects of Calcium on Absorption and Distribution of Ions and H+-ATPase Activity in Barley and Wheat Under Salt Stress

Calcium decreased Na+ absorption and transportation to the shoots,increased K+ and Ca2+ absorption and transportation ,decreased the leakage of electrolyties,and increased the accumulation of dry matter in barley and wheat seedlings under NaC1 stress. Calcium ion promoted the H+-ATPase activities in plasma membrane and tonoplast vesicles isolated from the young roots of the two plants, and increased respiration of the roots. This is in consistent with the results that calcium regulates ion absorption and distribution via its enhancement of H+-ATPase activities in plasma membrane and tonoplast.     

The effect of acetylcholine on growth and on growth inhibition by CCC in wheat seedlings

Summary The inhibition of the growth of wheat seedlings by 2-chloroethyltrimethylammonium chloride (CCC) was strongly reduced by root application of acetylcholine (Ach). Ach was applied after uptake of CCC by the roots or by the leaves. Ach also stimulated growth of non-CCC-treated seedlings up to 30% when applied to the roots. Growth stimulation appeared to be dependent on pH of the medium and most effective at pH 4.5 and 6. At pH 7.5 Ach did not promote growth of wheat seedlings.Organization for Applied Scientific Research.—Author's business address: Stichting, Centrum voor Plantenfysiologisch Onderzoek, C.P.O., Postbus 52, Wageningen, The Netherlands.     

Phytotoxic, clastogenic and bioaccumulation effects of the environmental endocrine disruptor bisphenol A in various crops grown hydroponically

The effects of the endocrine disruptor bisphenol A (BPA) at concentrations of 10 and 50 mg l⁻¹ were evaluated on the germination and morphology, micronuclei (MN) content in root tip cells and BPA bioaccumulation of hydroponic seedlings of broad bean (Vicia faba L.), tomato (Lycopersicon esculentum Mill.), durum wheat (Triticum durum Desf.) and lettuce (Lactuca sativa L.) after 6 and 21 days of growth. In general, BPA at any dose used did not inhibit germination and early growth (6 days) of seedlings of the species examined, with the exception of primary root length of tomato which decreased at the higher BPA dose. In contrast, an evident phytotoxicity was induced by BPA in all species after 21 days of growth with evident morphological anomalies and significant reductions of the lengths and fresh and dry weights of shoots and roots of seedlings. With respect to the nutrient medium without seedlings, BPA concentration decreased markedly during the growth period in the presence of broad bean and tomato seedlings, and limitedly in the presence of durum wheat and, especially, lettuce. Further, the presence of BPA measured in roots and shoots of broad bean and tomato after 21-day growth indicated that bioaccumulation of BPA had occurred. The number of MN in broad bean and durum wheat root tip cells increased markedly by treatment with BPA at both concentrations, thus suggesting a potential clastogenic activity of BPA in these species.     

Effect of zinc supply on growth of three species of Eucalyptus seedlings and wheat

Summary Effects of zinc supply on shoot and root dry weight, root length, zinc concentrations and carbonic anhydrase activity were measured in 52 day old seedlings ofEucalyptus maculata, E. marginata, E. patens and wheat grown in a zinc deficient soil in the glasshouse.Symptoms of zinc deficiency in the eucalyptus and wheat appeared within 20 to 35 days. Eucalypt seedlings had short internodes and small necrotic leaves, reduced dry weight of shoots and roots, root length and zinc concentrations in young leaves; the measurable level of leaf carbonic anhydrase activity decreased to zero. Similar responses also occurred in wheat.The level of zinc fertilizer required for normal growth of Eucalyptus seedlings is therefore likely to be similar to that used for wheat and other agricultural crops.     

Extracellular ATP induces ion fluxes and inhibits growth of Friend erythroleukemia cells

Extracellular ATP (1 mM) inhibited the growth of Friend virus-infected murine erythroleukemia cells (MEL cells) but had no effect on dimethyl sulfoxide-induced differentiation. ATP (1 mM) also caused changes in the permeability of MEL cells to ions. There was an increased influx of 45Ca2+ from a basal level of 5 pmol/min to 18 pmol/min/10(6) cells to achieve a 2-fold increase in steady-state Ca2+ as measured at isotopic equilibration. Ca2+ influx was blocked by diisothiocyanostilbene disulfonate (DIDS), an inhibitor of anion transport. ATP also stimulated Cl- uptake, and this flux was inhibited by DIDS. The ratio of ATP stimulated Cl- to Ca2+ uptake was 1.6:1. K+ and Na+ influx were also stimulated by ATP, but phosphate uptake was inhibited; the Na+ influx dissipated the Na+ gradient and thus inhibited nutrient uptake. ATP-stimulated K+ influx was ouabain inhibitable; however, the total cellular K+ decreased due to an ATP-stimulated ouabain-resistant K+ efflux. Na+ influx and Ca2+ influx occurred by separate independent routes, since Na+ influx was not inhibited by DIDS. The effects observed were specific for ATP *K1/2 MgATP = 0.7 mM) since AMP, GTP, adenosine, and the slowly hydrolyzable ATP analogue adenyl-5'-yl imidodiphosphate were without effect. The major ionic changes in the cell were a decrease in K+ and increase in Na+; cytoplasmic pH and free Ca2+ did not change appreciably. These ATP-induced changes in ion flux are considered to be responsible for growth inhibition.     

Changes in the pool of soluble sugars induced by dehydration at the heterotrophic phase of growth of wheat seedlings

Loss of dehydration tolerance coincides with a shift from heterotrophy to autotrophy during post-germination growth of spring wheat seedlings. This critical stage falls on the fifth day following imbibition. Till the sixth day of experiment light had no effect on dry weight of the seedlings but the survival of six day old seedlings was reduced by half upon dehydration. Germinating seeds in the presence of 5 mM glucose, fructose, mannose or sucrose did not promote seedling growth but either increase (glucose, fructose) or decreased (mannose, sucrose) the survival of dehydrated seedlings. Protection against dehydration by the former sugars was correlated, irrespective of the seedling age, with the decrease of sugar pool in seeds and increase in shoots (coleoptile and first leaf) and roots. The opposite changes were provoked by the sugars hampering seedling survival. Generally, survival of wheat seedlings was not correlated with the size of soluble sugar pool but its distribution and composition. Lower mobilisation of soluble sugars in seed, lower proportion of reduced sugars to sucrose and higher share of raffinose is characteristic for the tolerant four day old seedlings and those grown in the media containing glucose or fructose. The results presented indicate that higher proportion of reduced sugars to sucrose and lower share of raffinose in six day old seedlings seems to be associated with the loss of dehydration tolerance of these seedlings, despite heterotrophic character of growth.     

Activation by lithium ions of the inside sodium sites in (Na+ + K+)-ATPase.

1. Purified pig kidney ATPase was incubated in 30--160 mM Tris-HCl with various monovalent cations. 130 mM LiCl stimulated a ouabain-sensitive ATP hydrolysis (about 5% of the maximal (Na+ + K) activity), whereas 160 mM Tris-HCl did not stimulate hydrolysis. Similar results were obtained with human red blood cell broken membranes. 2. In the absence of Na+ and with 130 mM LiCl, the ATPase activity as a function of KCl concentration showed an initial slight inhibition (50 micrometer KCl) followed by an activation (maximal at 0.2 mM KCl) and a further inhibition, which was total at mM KCl. In the absence of LiCl, the rate of hydrolysis was not affected by any of the KCl concentrations investigated. 3. The lithium-activation curve for ATPase activity in the absence of both Na+ and K+ had sigmoid characteristics. It also showed a marked dependence on the total LiCl + Tris-HCl concentration, being inhibited at high concentrations. This inhibition was more noticeable at low LiCl concentrations. 4. In the absence of Na+, 130 mM Li+ showed promoted phosphorylation of ATPase from 1 to 3 mM ATP in the presence of Mg2+. In enzyme treated with N-ethylmaleimide, the levels of phosphorylation in Li+-containing solutions, amounted to 40% of those in Na+- and up to 7 times of those in K+-containing solutions. 5. The total (Na+ + K+)-ATPase activity was markedly inhibited at high buffer concentrations (Tris-HCl, Imidazole-HCl and tetramethylammonium-HEPES gave similar results) in cases when either the concentration of Na+ or K+ (or both) was below saturation. On the other hand, the maximal (Na+ + K+)-ATPase activity was not affected (or very slightly) by the buffer concentration. 6. Under standard conditions (Tris-HCl + NaCl = 160 mM) the Na+-activation curve of Na+-ATPase had a steep rise between 0 and 2.5 mM, a fall between 2.5 and 20 mM and a further increase between 20 and 130 mM. With 30 mM Tris-HCl, the curve rose more steeply, inhibition was noticeable at 2.5 mM Na+ and was completed at 5 mM Na+. With Tris-HCl + NaCl = 280 mM, the amount of activation decreased and inhibition at intermediate Na+ concentrations was not detected.     

Effect of salinisation of soil on growth and macro- and micro-nutrient accumulation in seedlings of Acacia catechu (Mimosaceae)

The effects of salinisation of soil on Acacia catechu (Mimosaceae) were studied by means of emergence and growth of seedlings and pattern of mineral accumulation. A mixture of chlorides and sulphates of Na, K, Ca and Mg was added to the soil and salinity was maintained at 4.1, 6.3, 8.2,10.1 and 12.2 dSm⁻¹. A negative relationship between proportion of seed germination and salt concentration was obtained. Seedlings did not emerge when soil salinity exceeded 10.1 dSm⁻¹. Results suggested that this tree species is salt tolerant at the seed germination stage. Seedlings survived and grew up to soil salinity of 10.1 dSm⁻¹, which suggests that this species is salt tolerant at the seedling stage too. Elongation of stem and root was retarded by increasing salt stress. Among the tissues, young roots and stem were most tolerant to salt stress and were followed by old roots and leaves, successively. Leaf tissue exhibited maximum reduction in dry mass production in response to increasing salt stress. However, production of young roots and death of old roots were found to be continuous and plants apparently use this process as an avoidance mechanism to remove excess ions and delay onset of ion accumulation in this tissue. This phenomenon, designated “fine root turnover”, is of importance to the mechanisms of salt tolerance. Plants accumulated Na in roots and were able to regulate transfer of Na ions to leaves. Stem tissues were a barrier for translocation of Na from root to leaf. Moreover, K was affected in response to salinity; it rapidly decreased in root tissues with increased salinisation. Nitrogen content decreased in all tissues (leaf, stem and root) in response to low water treatment and salinisation of soil. Phosphorus content significantly decreased, while Ca increased in leaves as soil salinity increased. Changes in tissue and whole plant accumulation patterns of the other elements tested, as well as possible mechanisms for avoidance of Na toxicity in this tree species during salinisation, are discussed.     

Effect of salinity and temperature on germination, growth and ion relations of Panicum turgidum Forssk

Seed germination of Panicum turgidum was significantly affected by salinity levels, temperature and their interaction. Maximum germination was noted in the lowest saline media (25-50 mM) and distilled water at the temperature of 15-25 degrees C and 20-30 degrees C. Seeds germination was substantially delayed and reduced with an increase in NaCl to levels above 50mM. This trend was much pronounced under high levels of NaCl and incubation temperature. Low levels of NaCl (25-50 mM) stimulated shoot and root dry weights of P. turgidum seedlings. However, the highest NaCl levels (>100 mM) resulted in a significant decrease in shoot, root and total dry weights of seedlings. Intermediate degrees of temperature, 15-25 and 20-30 degrees C, resulted in a significant increase in biomass accumulation. The Na+ concentration in shoots and roots significantly increased as NaCl concentration increased. The K+ concentration in roots and K/Na ratio in shoots and roots was significantly reduced as salinity concentration increased. The K/Na ratio was greatly affected by higher NaCl concentration and incubation temperatures.     

Effect of heavy metal ions on growth and biochemical characteristics of photosynthesis of barley and maize seedlings

The effects of Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ on growth and the biochemical characteristics of photosynthesis were more expressed in barley (Hordeum vulgare L.) than in maize (Zea mays L.) seedlings. The barley and maize seedlings exhibited retardation in shoot and root growth after exposure of Cu²⁺, Cd²⁺ and Pb²⁺. The Zn²⁺ions practically did not influence these characteristics. The total protein content of barley and maize roots declined with an increase in heavy metal ion concentrations. The protein content of barley shoots was only slighly decreased with an increase in heavy metal ion concentrations, but the protein content in maize shoots was increased under the same conditions. The chlorophyll content was decreased in barley shoots and increased in maize. The ribulose-l,5-bisphosphate carboxylase (RuBPC, EC 4.1.1.39) and phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) activities were decreased drastically by Cu²⁺, Cd²⁺ and Pb²⁺ in thein vivo experiments. The tested heavy metal ions affect photosynthesis probably mainly by inhibition of these key carboxylating enzymes: this mechanism was studied in thein vitro experiments.     

The site of action of lithium ions in morphogenesis of Lymnaea stagnalis analyzed by secondary ion mass spectroscopy

Abstract. Exogastrulation as a disturbance of development in eggs of Lymnaea stagnalis is caused by the action of LiCl at the second cleavage stage and not at the first or third. The percentage of exogastrulae formed is strongly concentration dependent. To determine the site of action of lithium ions, the cellular contents of Li, C, Na, Mg, P, K, and Ca were analyzed by secondary ion mass spectroscopy (SIMS). The mean elemental concentrations of Na, Mg, K, and Ca are close to those found earlier by electron probe microanalysis and atomic absorption spectroscopy. Lymnaea eggs at the first, second, and third cleavage stage were treated with LiCl in a series of concentrations ranging from 50 to 0.1 mM. In all cases the cells contained a few mM lithium after treatment. After treatment at the insensitive first cleavage stage the lithium content is carried over by the cells through the sensitive second cleavage to the insensitive third cleavage stage. These data allow the conclusion that it is the external lithium concentration which is responsible for the specific effect. This presents direct analytical evidence that the primary action of lithium ions is located at the cell membrane.